Bobbin case carrier for sewing machines



July 31, 1962 L. J.-KU

BOBBIN CASE CARRIER FOR SEWING MACHINES Filed May 19, 1958 INVENTOR.Ludwig Kuhar I BY Figs. 7 ATTORNEY United States Patent ()fificePatented July 31, 1962 3,046,922 BOBBIN CASE CARRIER FOR SEWING MACHINESLudwig J. Kuhar, Clark Township, N.J., assignor to The SingerManufacturing Company, Elizabeth, N.J., a corporation of New JerseyFiled May 19, 1958, Ser. No.,736,160 3 Claims. or. 112-431 The presentinvention relates to a bobbin case carrier of a sewing machine and moreparticularly to the formation of the rotation restraining notch in thebobbin case carrier of a sewing machine.

In a lock stitch sewing machine of the rotary hook type, the bobbin ismounted in a bobbin case that is in turn inserted in a bobbin casecarrier which is mounted in the body of the rotary hook for rotation ofthe hook relatively to the bobbin case carrier. During operation of thesewing machine, the bobbin case carrier is restrained against rotationwhile the hook is rotated relatively thereto to seize and cast a loop ofneedle thread about the bobbin case carrier. Since the needle threadloop must pass completely around the bobbin case carrier, the rotationrestraining means must allow for passage of the thread between therotation restraining means and the bobbin case carrier. In theconventional manner, the rotation restraining means comprises a fingermounted in the bed of the machine and having a tongue that is seated ina notch in the face of the bobbin case carrier. This invention relatesspecifically to the formation of this rotation restraining notch in thebobbin case carrier and has for an object to form this notch in such amanner as to facilitate manufacture.

Having in mind the above and other objects that will be evident from anunderstanding of this disclosure, the invention comprises the devices,combinations and arrangements of parts as illustrated in the presentlypreferred embodiment of the invention which is hereinafter set forth insuch detail as to enable those skilled in the art readily to understandthe function, operation, construction and advantages of it when read inconjunction with the accompanying drawings in which:

FIG. 1 is a plan view of a bobbin case carrier for a rotary hook of asewing machine, which bobbin case carrier embodies the presentinvention, l

FIG. 2 is a fragmentary sectional view taken substantially on the line2-2 of FIG. 1,

FIG. 3 is a fragmentary plan view similar to FIG. 1 and illustrating theprior art.

The present invention is herein disclosed as applied to a bobbin casecarrier of a conventional type of rotary hook which is illustrated, forexample, in the United States patent of Kessler, No. 2,085,699, to whichreference may be had for an understanding of the function and operationof the bobbbin case carrier.

As illustrated in the drawings, the bobbin case carrier is cup-shapedand comprises a cylindrical side Wall 1 which, to reduce the mass, hasan open back that is spanned by a diameter bar 2. The bar 2 supports acentrally located stud '3 for mounting and latching the bobbin casewithin the carrier.

For journaling the bobbin case carrier within the raceway of a rotaryhook, there is provided a peripheral hearing rib 4 on the outer surfaceof the side wall 1. The bearing rib 4 is discontinuous to provide athread loop detaining shoulder 5 and a loop confining shoulder 6. On theneedle thread loop cast off side, there is provided on the top of theside wall 1, a laterally extending loop controlling fiange 7 thatextends beyond the top center of the carrier and at the top thereof isprovided with a notch 8 for receiving the tongue of a rotationrestraining finger (not shown). On the cast on side of the bobbin caseaway at 10 and has a bore 11 to provide for needle clear- I ance.

With reference to FIG. 3, there is illustrated a bobbin case carrierconstruction in accordance with the prior art methods and which includesa rotation restraining notch 30. In the prior construction, the rotationrestraining notch 8a was formed in three successive milling operations.In the first operation, a slot is milled in the face of the flange 7 bya relatively wide cutter that passes straight across the face of theflange 7 substantially ra dially of the bobbin case carrier, thusproducing the side walls 12 and the bottom 13 of the notch 8a. To avoidthe sharp corners of the inner end of the side walls 12 that result fromthe first milling operation, over which corners the thread is drawnduring the sewing operation, the inner ends of the side walls 12 wereflared or beveled outwardly by means of relatively narrow cutters in thetwo subsequent milling operations. These cutters were passed through theslot at an angle to the center line of the slot, thus producing the sidewalls 14 and 15 and the respective bottoms 16 and 17.

Within the limitations of reasonably economical manufacturing processes,the cutters in the milling operations cannot be held to exactly the samedepths with the result that the bottoms 13, 16 and 17 do not coincide,or in other words, do not define a single continuous planar bottom forthe notch 8a. In FIG. 3, there is illustrated the condition that resultswhen the left hand cutter is set at a depth slightly less thm the depthof the initial straight cutter and the right hand cutter is set at adepth slightly greater than the depth of the initial cutter. In thiscase, the bottom 16 is above the bottom 13 with a resulting edge 18 atthe meeting line, and the bottom 17 is below the bottom 13 and in effectcuts a groove in the bottom 13 which produces edges 19. p

Since during the sewing operation, the limb of the needle thread must beswung laterally across the notch 8a before the loop is withdrawn, thebottom of the notch 8a must be smooth and continuous, or in other words,without edges such as at 18 and 19 upon which the thread could catch orsnag and be thus held back. Thus, after milling in the priorconstruction, the bottom of the notch 8a had to be hand filed to removeany edges, such as 1-8 and 19, resulting from the milling operations.Because the notch 8a is only less than one eighth of an inch wide andbecause the post 3 is located only three eighths of an inch from theinner edge of the side wall 1, this filing operation is very delicateand difiicult. At the same time, and also because of the variations inthe resulting edges in the bottom of the notch 8a, this filing operationwas per formed by hand. It is obvious that finishing of the bottom ofthe notch 8a was an expensive operation.

In accordance with the present invention there has been provided abobbin case carrier in which the rotation restraining notch 8 is formedin such a manner as to eliminate the subsequent hand filing that isrequired in the prior art construction. As illustrated in FIGS. 1 and 2,the notch 8 in the present construction comprises an outer portion 20 inthe form of a slot having parallel side walls 21 and a planar bottom 22.The outer portion 20, like the slot formed in the first millingoperation in the prior art construction, is arranged substantiallyradially of the bobbin case carrier. To flare the inner ends of the slotoutwardly there is an inner portion 23 comprising a depression milled inthe face of the flange 7 to substantially the same depth as the outerportion 20 and having an inner edge which is defined by the coincidinginner edges of the side wall 1 and flange 7 and an outer edge whichouter portion 20 and arranged substantially centrally of V 3 V thecenter line of the outer portion 20. The inner portion 23 is thuscrescent-shaped and intersects the side walls 21 of the outer portion toprovide arcuate side edges 24 which constitute diverging side walls andthus act to flare outwardly the inner ends of the side walls 21 of theouter portion 20. The inner portion 23 includes a bottom 25 which, toavoid a sharp edge at its meeting line with the bottom Wall 22 isarranged at a slight angle to the plane of the bottom wall 22, the anglebeing illustrated at A in FIG. 2 and being substantially three degrees.Thus, the bottom walls 22 and 25 will always intersect along a line,such as 26, and will blend smoothly.

In the formation of the slot 8 in accordance with the present invention,the first operation is the same as in the prior construction, i.e., theflange 7 is first milled by a cutter that passes across the face thereofto provide a slot and thus form the outer portion 20 of the notch 8. Theslot is then flared, as illustrated in FIG. 2, by a circular end mill 27having a diameter greater than the diameter of the slot and advancedendwise onto said flange with the axis thereof arranged at an angle ofthree degrees to a line normal to the bottom wall 22 to form the innerportion 23 of the notch 8. Thus, the notch 8 has been completely formedin only two operations and without the necessity of a subsequent handfiling operation. Any variations in the depth of penetration of the endmill 27 from the designed optimum, while it may vary the position of theline 26 radially of the bobbin case carrier or may produce an edge alongthe line 26, it does not produce any appreciable edges lengthwise of thenotch 8 upon which the thread could snag as it moves laterally of thenotch 8.

Numerous alterations of the structure herein disclosed will suggestthemselves to those skilled in the art. However, it is to be understoodthat the present disclosure relates to a preferred embodiment of myinvention which is for purposes of illustration only and not to beconstrued as a limitation of the invention. All such modifications whichdo not depart from the spirit of the invention are intended to beincluded within the scope of the appended claims.

Having thus described the nature of the invention, what I claim hereinis:

1. A bobbin case carrier for a sewing machine having a cylindrical sidewall and a laterally extending flange on the top of said side Wall andhaving a rotation restraining notch formed in the face of said flange,said notch comprising an outer portion having a planar bottom andparallel side walls extending generally radially relatively to saidbobbin case carrier, and an inner portion having side Walls diverginginwardly and intersecting and constituting bevels on the inner ends ofthe side walls of said outer portion and a planar bottom arranged at aslight angle to the bottom of said outer portion. 7

2. A bobbin case carrier for a sewing machine having a cylindrical sidewall and a laterally extending flange on the top-of said side wall andhaving a rotation'restraining notch formed in the face of said flange,said notch coniprising an outer portion having a planar bottom andparallel side walls extendinggenerally radially relatively tgo saidbobbin case carrier, and a crescent-shaped inner portion having arcuateside walls intersecting and constituting bevels on the inner ends of theside walls of said outer' portion and a planar bottom arranged ataslight angle to the bottom of said outer portion.

3. A bobbin case carrier for a sewing machine having a a cylindricalside wall and a laterally extending flange on the top of said side Walland having a rotation restraining notch formed in the face of saidflange, said notch comprising an outer portion having a planar bottomdisposed in a plane substantially normal to the am's of said bobbin casecarrier and parallel side walls extending generally Y radiallyrelatively to said bobbin case carrier, and an inner portion having sidewalls diverging inwardly and intersecting and constituting bevels on theinner ends of the side walls of said outer portion and a planar bottomarranged at a slight angle to the bottom of said outer portion andinclined radially inwardly of the bobbin case carrier toward theopposite face of said flange from said notch.

References Cited in the file of this patent UNITED STATES PATENTSWertepny et a1. June 30,

